Dyslipidemia in Achilles Tendinopathy Is Characteristic of Insulin Resistance

Overuse is considered to be a main causative factor for tendinopathies; however, recent reports indicate that tendinopathy is also common among both overweight and inactive individuals. These factors are associated with abdominal obesity, dyslipidemia, hypertension, and insulin resistance. We hypothesized that these features would be associated with tendinopathy. To compare lipid profile between participants with Achilles tendinopathy and matched controls. Fasting serum lipids were measured among 60 participants with chronic painful midportion Achilles tendinopathy (54% male) and 60 control subjects matched for gender, age (+/-10 yr), and body mass index (+/-2 kg x m(-2)). The participants with Achilles tendinopathy showed evidence of underlying dyslipidemia. They had higher triglyceride (TG) levels (P = 0.039), lower %HDL-C (P = 0.016), higher TG/HDL-C ratio (P = 0.036), and elevated apolipoprotein B concentration (P = 0.017) in comparison to the well-matched control group. This pattern of dyslipidemia is characteristic of the dyslipidemia displayed by individuals with insulin resistance and is common in the metabolic syndrome. Two additional aspects of tendinopathy research support a connection with the metabolic syndrome. First, tendinopathy has been associated with greater waist circumference, as has the metabolic syndrome. Second, insulin resistance has been associated with fat deposition in muscle (primarily intracellular), whereas fat deposition in tendon has been found among those with tendon pain.If tendinopathy is confirmed to be associated with dyslipidemia and the metabolic syndrome in larger studies, it may be appropriate to redefine our concept of tendinopathy to that of a cardiovascular disease (CVD). In this case, we may be able to draw considerably on CVD research to improve our understanding of tendinopathy, and perhaps treating CVD risk factors will improve the treatment of tendinopathy.